To answer all of your questions very briefly:
* Hero shards are part of heroes themselves. The easiest way is to roll them with 10x rolls.
A more reliable way but expensive way is getting them through the alchemy workshop.
* Glory eggs used to be obtained through Lords gone wild and Wishing tree event. These are free to play events but I do not see them (glory eggs) returning anytime soon. So for now: 10x rolls.
* A healer really depends on the team you are using and is too broad to answer. See what fits your team. The best healers in my opinion are Abyss Demon, Ambrosia and Toxic Shaman respectively.

@Dragoneyr
Thanks for your reply!
it seems this game has a fairly inactive forum and lots of spam from those website thingies :/
My account is from like 3 or 4 years ago so im obviously far behind and I have a bit of trouble getting back up to speed so i kind of need to figure everything out rn.
Is it the same as with castle clash, that all the new heroes are OP and i should focus on them if i get them?

This forum was very active earlier. In last six months many good players/moderators got fed up by IGGs greedy policies and quit. So this forum is almost dead now. Dragoneyr is one of few people who is still active and gives good advice. New heroes are OP but they are hard to get/evolve, unless you are a big spender. For a f2p, amb GS AD PG RV ench wolv are best bang for ur buck. Berz is a must have aid. Pg sm BH CHiron ench are other very good aids. You can make many different combinations of these heroes/aids to make good teams. There is no single set of 5 heroes which are best in all modes. You have to choose different fives in different modes.

I'd suggest you concentrate on weapons. Heroes come and go, but weapons are always useful. Best thing I ever did as f2p was work on my weapons and got them to a reasonable level. I think I have 7 level 3 gold/orange weapons now and a couple lower level gold/orange weapons. Took a while but my power is approaching 9000. That made more of a difference than any single hero. I would not waste glory eggs on Pan. Pan is easy to get shards for and easy to glory. I am high on abyss, toxic and amber who all heal. They will remain relevant for a long time. Save glory eggs for Wonder Woman!